1. Technical Field
The present invention relates to a turning drive device for driving a turning body arranged at a construction machine and similar machinery.
2. Description of Related Art
Construction machines such as excavators generally include a drive device for driving a turning body to which a work element such as a bucket is mounted. For example, in an excavator, a bucket corresponding to a work element may be mounted to an upper turning body where a cabin is arranged so that the bucket may turn along with the turning motion of the upper turning body. In this way, the bucket may be turned around the excavator and moved to a desired position where work is to be performed. The excavator includes a turning mechanism for driving and turning the upper turning body.
Such a turning mechanism may use a turning motor as a drive source. Power supply to the tuning motor is controlled by an inverter. The inverter is controlled by a controller that controls overall operations of the drive mechanism of the excavator. When an abnormality occurs at the controller itself or within a control signal line between the inverter and the controller, the controller may no longer be able to control the inverter, and as a result, normal drive operations of the turning mechanism may become impossible.
In this respect, a technique is known in which a subordinate control unit (e.g., inverter) monitors a superordinate control unit (e.g., controller) for an abnormality, and the subordinate control unit, upon detecting an abnormality in the superordinate control unit, controls the drive device.